Polymers & polymerization
Published on: Mar 4, 2016
Transcripts - Polymers & polymerization
Name: Vijay Kumar
Types of polymerization
A word polymer is a combination of two Greek words, “Poly” means “many” and “Mer” meaning “
part or unit”.
A polymer is a large molecule of which is formed by repeated linking of the small molecules called
More monomer molecules joined in units of long polymer.
Classification Based On Source.
Classification Based On Structure.
Classification Based On Polymerisation.
Classification Based On Molecular Force.
1. natural polymers:- The definition of a natural polymer is a polymer that results
from only raw materials that are found in nature.
Example:- proteins, cellulose, starch, rubber.
2. semi-synthesis polymers:- Cellulose derivatives as cellulose acetate
(rayon) and cellulose nitrate etc. are the usual examples.
3. synthesis polymers:- A variety of synthetic polymers as plastic synthetic
fibers are examples of manmade polymers.
Example:- Buna-s, buna-r, nylon, polythene, polyester.
1. Linear polymers:- Consist of long and straight chains. Example:- pvc
2. Branched chain polymers:- contain linear chains having some branches, e.g., low
3. Cross linked chain polymers:- formed from bi-functional and tri-functional monomers
and contain strong covalent bonds e.g. bakelite, melamine.
Linear Branched Cross-linked
1. Addition polymers:- Formed by the repeated addition of monomer molecules
possessing double or triple bonds.
n(CH2=CH2) -(CH2 -CH2 )-
2. Condensation polymers:- Formed by repeated condensation reaction between two
different bi-functional or tri-functional monomeric units.
Example: Terylene (dacron), nylon 6, 6, nylon 6.
n(H2N(CH2)6 NH2) + n(HOOC(CH2)4COOH) [-NH(CH2)6NHCO(CH2)4CO-]n + nH2O
1. Elastomers :- These are rubber-like solids with elastic properties.
The polymer chains are held together by the weakest
intermolecular forces. A few cross links are introduced in
between the chains, which help the polymer to retract to its
original position after the forces is released as in vulcanized
example: Buna-S, Buna-N, Neoprene etc.
2. THERMOPLASTIC POLYMERS:-
These are linear or slightly branched long chain polymers, which can be
softened on heating & reversibly hardened on cooling repeatedly. Their
hardness is a temporary property & varies with temperature.
EXAMPLE:- POLYVINYL CHLORIDE.
POLYVINYL CHLORIDE:- It is a vinyl polymer constructed of repeating vinyl
groups (Ethenyls) having one of their hydrogens replaced with a
3. THERMOSETTING POLYMERS:-
Initial mixture of reactive, low molar mass compounds reacts upon
heating in the mold to form an insoluble, infusible network.
BAKELITE: Bakelite is formed of phenol and form-aldehyde polymerization.
1. Addition polymerization:-
The polymer is formed from the monomer, without the loss of any material, and
the product is the exact multiple of the original monomeric molecule.
Addition polymerization proceeds by the initial formation of some reactive
species such as free radicals or ions and by the addition of the reactive species to
the other molecule, with the regeneration of the reactive feature.
1. Free radical mechanism:- Alkenes or dienes and their derivatives are polymerized in
the presence of a free radical generating initiator (catalyst) like benzoyl
peroxide, acetyl peroxide, t-bu peroxide, etc.
This process involves three steps:-
a) Chain initiation step - addition of phenyl free radical formed by the peroxide to the ethene double
bond ,thereby forming a larger radical.
b) Chain propagation step - Repetition of this sequence with new and bigger radicals.
c) Chain terminating step - The product radical thus formed reacts with another radical to form the
Process in which two monomers react to form a larger molecule and
eliminate a smaller molecule (usually water, ammonia, methanol or
It also called as step-growth polymerization.
EXAMPLE:- 1. POLYAMIDE:- NYLON 6-6, NYLON 6.
2. POLYESTER:- TERILIN
3. BAKELITE POLYMER
4. MALEMIN POLYMER
Characteristics of polymer
Low coefficient of friction.
Good corrosion resistance.
Good mould ability.
Excellent surface finish can be obtained.
Can be produced with close dimensional tolerances.
Poor tensile strength.
Low mechanical properties.
Poor temperature resistance.
Can be produced transparent or in different colours.
Application of polymers
1. Medicine:- Many biomaterials, especially heart valve replacements and
blood vessels, are made of polymers like Dacron, Teflon and
2. Consumer Science :- Plastic containers of all shapes and sizes are light weight
and economically less expensive than the more traditional containers.
Clothing, floor coverings, garbage disposal bags, and packaging are
other polymer applications.
3. Industry:- Automobile parts, windshields for fighter planes, pipes, tanks,
packing materials, insulation, wood substitutes, adhesives, matrix for
composites, and elastomers are all polymer applications used in the
4. Sports:- Playground equipment, various balls, golf clubs, swimming
pools, and protective helmets are often produced from polymers.